The traffic density in the worldwide road networks increases significantly every year. Freeways and expressways are particularly affected. In particular during bad weather, the full attentiveness of the driver is required to orient himself in traffic. The recognition of other road users in case of fog or high air humidity represents a big problem in particular. In this case, the other road users are often only recognizable with the aid of the existing headlights. Particularly the spray mist arising in wet weather causes the vehicle contours of the preceding vehicles and the following vehicles to blur, and the visibility may drop significantly in spite of activated headlights. Current developments allow the headlights to be turned on automatically as a function of the applicable light and weather conditions.
A device for automatically setting the luminance of a light beam emitted from at least one rear illumination device of a vehicle as a function of the brightness and the range of vision in the surroundings of the vehicle is known from DE 102 05 184 A1, which has a sensor device for ascertaining the brightness and the range of vision in the vehicle's surroundings.